This invention relates to a cable splice for an electrical cable and to a method for making a cable splice. More particularly, this invention relates to a cable splice for use in high temperature, high pressure gassy oil wells adapted to prevent depressurization-caused rupture failures, and to a method for making said cable splices.
In general, cable structures employed for oil well service have stranded metallic conductors, usually formed of copper, separately insulated with a material of high dielectric strength, cabled and surrounded by an outer armor. In joining cable sections, a splice is formed between the conductors comprising a metallic member frictionally engaging the conductors and a section of insulant surrounding the exposed ends of the conductors and the metallic member which forms the primary insulation of the splice. The section of insulant typically is formed by a plurality of layers of insulating tape, and may be surrounded and confined by a heat shrinkable sleeve positioned over the primary insulation and extending over the adjacent insulation to seal the splice area.
Where the well cable is to be employed in particularly gassy wells, invasion of the splice area by low molecular weight well fluids under high pressure occurs either by way of pinholes or other defects in the primary insulation of the splice or by gas permeation. When the cable is removed from the well bore, the external pressure is decreased creating an unbalanced high pressure condition within the splice structure, due to the presence of low molecular weight hydrocarbons. Mechanical destruction of the splice insulation by blow-out or rupture failure often results.